1. Field
This disclosure relates to an optical packet switching apparatus and an optical packet switching method for switching over a path of an optical packet signal.
2. Description of the Related Art
Currently, a WDM (Wavelength Division Multiplexing) transmission is the dominant form of trunk optical communication network system. In the future, from the viewpoint of increasing the network use efficiency, an optical packet switching network is expected in which an optical signal has a smaller granularity. A path of an optical packet may be switched over on the order of a micron-second to a nano-second, instead of a second to a millisecond, while the signal is kept in the state of light.
A large-scaled (N×N)-matrix optical packet switching apparatus capable of performing multi-dimensional connections is needed to realize the optical packet switching apparatus in the WDM transmission system. However, such an optical packet switching apparatus is not yet practical. In trying to realize the multi-dimensional connections by connecting many small-scaled optical packet switching apparatuses in multiple stages, a large number of optical packet switching apparatuses and various optical parts are needed. Therefore, realizing the multi-dimensional connections is difficult with respect to size and cost.
In the optical packet switching network to be realized for enabling a wide-band and flexible network construction, a delivery/coupling optical switching apparatus is proposed in which elements for switching over small-scaled optical switches at high speed, or SOAs (Semiconductor Optical Amplifiers) for turning on/off the optical signals, etc. are connected in multiple stages.
In the above-described delivery/coupling optical switching apparatus, a branch loss is compensated for by amplifying an optical signal with an amplifier, e.g., an EDFA (Erbium-Doped Fiber Amplifier), whenever the optical signal is branched by each of (1:X)-branch coupler which are connected in a cascaded manner to minimize deterioration of an optical SN (Signal/Noise) ratio.
On the other hand, a wavelength-selective optical switching apparatus is proposed in which a plurality of wavelength variable transmitters and wavelength multiplexers/demultiplexers are utilized to realize multi-dimensional connections by assigning a wavelength per port (see, e.g., Japanese Laid-open Patent Publication No. 5-244649).